VWF concatemerization proceeds through a disulfide exchange mechanism. (A) Overview showing the juxtaposition of domains D′-A1 from separate molecules in the center of a single bead. (B-C) Arrangement of intra- and intermolecular disulfide bonds in VWF tubules generated with dimeric D1-A1. (D-E) Arrangement of interfacial cysteines and intramolecular disulfide in VWF tubules generated with monomeric D1-A1. (F) Superposition of D3 domains showing the rearrangement of the 1091-1097 loop between monomer and dimer states. Model superposition was performed using the matchmake function of ChimeraX.